The present invention relates to an image forming apparatus to form an image on a recording material, and to an image reading device to read out the image of a document.
A digital copier is, in its function, structured by the image forming apparatus to form an image on a recording material, and an image reading device to read out the image of the document. In the digital copier, various control circuits are used. For example, there are a writing control circuit to control a writing section to conduct writing according to the image data, a photoelectric conversion control circuit to control a photoelectric conversion section to receive the light from the document and photoelectrically convert it, a reading image processing circuit to image process the image data output from the photoelectric conversion section, an operation control circuit to control an operation section, a sequence control circuit to control the sequence of the overall image forming apparatus, and an ADF control circuit to control an automatic document feeding apparatus. These control circuits are driven by using, for example, a quartz oscillator, by a clock signal synchronized with a predetermined frequency, and the data is transferred between respective control circuits, and reading out of the image data or image formation are conducted. The clock signal is one of the largest generation sources of the electromagnetic interference, so called EMI. As the countermeasure for it, conventionally, various countermeasures are taken in the manner that these control circuits are surrounded by a frame body, or the similar manner, however, it is an actual situation that these are not yet satisfactory.
As a countermeasure for the EMI of the clock signal, a technology which recently attracts one's attention is a technology in which the Spectrum Spreading clock (SSC) theory is applied on the Spectrum Spreading clock generator (SSCG). This technology can spread the band of the synchronized clock signal, and thereby, can attenuate the peak radiation of the fundamental wave or the higher harmonics. FIG. 6 is a view in which the horizontal axis shows the frequency and the vertical axis shows the electromagnetic wave radiant intensity, and is a view typically showing the spectrum spreading clock. As can clearly be sheen FIG. 6, to the waveform of the synchronized clock (broken line) before spreading, in the spectrum spreading clock which is modulated and spread, the intensity becomes low.
As described above, the SSCG is effective for the EMI countermeasure, however, when the present inventors apply this onto the image forming apparatus or image reading device as it is, various problems are found. For example, various problems are generated as follows: fine image recording can not be conducted, or image recording can not be finely conducted, or image reading can not be finely conducted, and further, the matching among various control circuits can not be obtained.